Embodiments of the present invention generally relate to neurostimulation systems, and more particularly to methods and systems to monitor an implanted lead and implanted neurostimulation device.
Neurostimulation (NS) systems are systems that generate electrical pulses and deliver the pulses to nerve tissue to treat a variety of disorders. Spinal cord stimulation (SCS) is the most common type of neurostimulation. In SCS, electrical pulses are delivered to nerve tissue in the spine typically for the purpose of chronic pain control. While a precise understanding of the interaction between the applied electrical energy and the nervous tissue is not fully appreciated, it is known that application of an electrical field to spinal nervous tissue can effectively mask certain types of pain transmitted from regions of the body associated with the stimulated nerve tissue. Applying electrical energy to the spinal cord associated with regions of the body afflicted with chronic pain can induce “paresthesia” (a subjective sensation of numbness or tingling) in the afflicted bodily regions. Thereby, paresthesia can effectively mask the transmission of non-acute pain sensations to the brain.
An NS system generally includes a NS device (NSD) that includes a pulse generator, with the NSD coupled to one or more stimulation leads. A stimulation lead includes a lead body of insulative material that encloses wire conductors. The distal end of the stimulation lead includes multiple electrodes that are electrically coupled to the wire conductors. The proximal end of the lead body includes multiple terminals, which are also electrically coupled to the wire conductors that are adapted to receive electrical pulses. The distal end of a respective stimulation lead is implanted within a desired area, such as the epidural space, to deliver the electrical pulses to the appropriate nerve tissue, such as within the spinal cord that corresponds to the dermatome(s) in which the patient experiences chronic pain. The stimulation leads are then tunneled to another location within the patient's body to be electrically connected with a pulse generator or, alternatively, to an “extension.”
The NS device is typically implanted within a subcutaneous pocket created during the implantation procedure. In SCS, the subcutaneous pocket is typically disposed in a lower back region, although subclavicular implantations and lower abdominal implantations are commonly employed for other types of neuromodulation therapies.
The NS device is typically implemented using a metallic housing that encloses circuitry for generating the electrical pulses, control circuitry, communication circuitry, a rechargeable battery, etc. The pulse generating circuitry is coupled to one or more stimulation leads through electrical connections provided in a “header” of the pulse generator. Specifically, feedthrough wires typically exit the metallic housing and enter into a header structure of a moldable material. Within the header structure, the feedthrough wires are electrically coupled to annular electrical connectors. The header structure holds the annular connectors in a fixed arrangement that corresponds to the arrangement of terminals on a stimulation lead.
After implantation, it may become desirable to monitor various parametric properties of the NS system. For example, it may be desirable to analyze the operation of the NS device, such as the discharge mode, pulse sequency, pulse width and frequency for the stimulation output of the NS device. Further, it may become desirable to locate the NS lead and more specifically, to locate the position and/or identity inoperative and operative electrodes on the NS lead. After implementation, the potential exists for NS leads to move or migrate within the patient. Heretofore, there has been no reliable and practical mechanism to readily identify lead migration. Also, there is no reliable and practical method for a physician or representative to locate the lead's position in connection with reprogramming or physical intervention. Today, physicians use fluoroscopy systems to locate a lead that has moved within the patient. Once the new position of the lead is identified, the physician then reprograms the lead, such as to use a different set of electrodes on the lead to deliver the stimulus output. This method exposes the patient to radiation each time a fluoroscopy is performed, which is not desirable.
Also, presently there is no reliable and practical way to identify lead malfunctions. Lead malfunctions may occur due to physical failure or breaks within the lead conduction and/or electrical failures within the NS device. Today when a physical failure or break causes a lead to operate intermittently or not at all, the intermittent and open leads are not easily diagnosable down to the electrode.
Further, today no tool exists that enables data logging for research to enable patient anomalies to be recorded in connection with stimulation outputs while an NS lead is in the patient. Also, today problems occur in the emergency medical field because an unconscious person cannot inform an EMT that the person has an implantable device, and cannot inform the EMT of the location of the implantable device. Hospitals using MRI's and X-ray machines may not have a quick method of determining what type of device the patient has within them, nor the location of the device.
A need remains for systems and methods that detect an implanted lead and/or an implanted neurostimulation device and that provide parametric information in connection therewith.